An individual's heart rate can have large impacts on the individual's health. It is well known that an individual's heart rate adapts to changes in the body's need for oxygen, which can be precipitated by exercise, rest, or other levels of activity. A change in heart rate also occurs in response to stressful stimuli, resulting from a release of adrenaline and cortisol, and concomitant with the heart rate increase is a redirection in blood flow to the muscular system, fat releases into the bloodstream for use as energy, increases in breathing rate, muscle tension, and increases in blood clotting ability. While these reactions may be beneficial in a fight-or-flight situation, these situations are uncommon; instead individuals are engaged in prolonged periods of stress caused by work, family, children, etc., that negatively affect their health.
Biofeedback techniques have been used to self-regulate heart rate. In general, biofeedback is a process that trains an individual to influence involuntary physiological functions for the purposes of improving health and performance. As some examples, biofeedback techniques have purportedly been used to treat migraine and tension headaches, digestive disorders, hypertension, hypotension, cardiac arrhythmia, Raynaud's, epilepsy, paralysis, movement disorders and chronic pain.
Evaluation of an individual's heart rate is typically done via a few different methodologies. A standard heart rate measurement is simply an assessment of the number of heart beats per unit of time, typically beats per minute (BPM). A more accurate, yet more difficult to measure, metric, is heart rate variability (HRV). HRV monitoring involves monitoring the heart beat rate and discerning the rate at which the heart beat rate changes. HRV may be monitored by detecting the individual's pulse and measuring the inter-beat interval (the “rise-rise interval” or RR interval).